Thermoplastic sheet pile design and methods of manufacture

ABSTRACT

A method of pre-assembling two standard Z-Shaped thermoplastic sheet pile segments in a factory controlled environment where the sheets are fused or welded by a process using heat and pressure, added material or pressure without heat to create a monolithic structure that is stronger than the individual sheets used to make the final assembly. By using two existing profile extrusions that individually can be used as is or pre-assembled in the field, product quality is assured by redundant quality checks. The first, when the sheet is produced and the second, when they are assembled and fused into one.

Applicants claim priority of U.S. Provisional Patent Application No. 60/679,753, filed May 11, 2005.

BACKGROUND OF THE INVENTION

The developments of seawall members have led to several patents that describe various shapes that take advantage of material properties to impart strength into the final linear product. The steel industry has traditionally supplied a Z-Shape pile with various types of male and female interlock designs allowing the sheet members to be joined together. Z-Shaped profile is a linear member with two offset parallel surfaces with a single connecting web or member. Steel sheet pile used as soil retaining devises for many years. Often these sheet members are welded together to achieve added strength or to prevent fluid from passing between the individual linear sections.

With the development of non-steel sheet piling (Hooper U.S. Pat. No. 5,145,287, Berger U.S. Pat. No. 4,690,588, Lewis U.S. Pat. No. 5,333,971, Wickberg U.S. Pat. Nos. 5,921,716 & 4,863,315, Irvine U.S. Pat. Nos. 6,000,883 & 6,033,155, Burt U.S. Pat. No. 6,575,667) several designs were introduced which again take advantage of the preferred material used. Fiberglass or thermoplastic type materials are used as they resist corrosion and decay. Burt describes a sheet with two planar surfaces with male and female interlocks located on opposing edges. This design offers an advantage over the Hooper and Irvine designs in that it uses the properties of thermoplastic materials to produce a sheet pile that is 24″ in width while maximizing the section modulus or panel stiffness.

DESCRIPTION OF THE INVENTION

The invention claims to use a plastic Z-Shape profile extruded sheet pile and produce a single sheet that can be installed using conventional installation methods. The design described by Burt, U.S. Pat. No. 6,575,667, solves certain economic issues by providing a 24″ wide panel with male/female edge interlocks. Installation crews would need to pre-assemble two smaller sheets and attempt to install two sheets at once. Often, they would drill a hole through the pre-assembled interlocks and use a nail to help keep the two sheets aligned when raised to a vertical position.

The present invention uses a machine to pre-assemble two standard Z-Shaped thermoplastic sheet pile segments in a factory controlled environment. The sheets are fused or welded by a process using heat and pressure to create a monolithic structure that is stronger than the individual sheets used to make the final assembly. By using two existing profile extrusions that individually can be used as is or pre-assembled in the field, product quality is assured by redundant quality checks. One, when the sheet is produced and one when they are assembled and fused into one.

The final product generally appears to be two pre-assembled sheets with a seam where the two sheets are fused together. Conventional plastic welding techniques are not sufficient to be of commercial value as the existing male/female interlocks make it difficult to melt the adjoining surfaces and add welding material The method of fusion requires that the surfaces or edges of fusion will not fail, when subjected to forces of shear in the direction of extrusion. It is an important subject of the present invention that the assembled sheets are fused sufficiently to assure this slippage of the interlocks even if subjected to enough force to cause the base sheet profile extrusion to fail. This assures that the section modulus calculations for both sheet pile extruded profiles are now treated as one sheet. The result being one sheet stronger than two individual sheets.

Another advantage of the present invention is that individual panels of different sizes, shapes, or brand names can be fused as one to create less expensive or stronger alternatives to what may be readily available.

The invention while producing a sheet pile segment that is slightly more expensive to produce than a comparable item using the Burt design, the production machinery need to produce the new item is significantly smaller and much less costly. Smaller capital investment enables satellite production facilities. A supply firm can minimize freight expense by producing finished product close to the geographic location of different customers or markets.

Thermoplastic sheet pile profile is readily available from several producers in the United States, Crane Materials International, Northstar and Weather-Ex Corporation. All produce and market a Z-Shaped profile of various sizes and colors. Two sheets are placed in a device that heats both edges in a controlled manner to avoid damage to the material. The edges of each sheet pile are heated enough to permit one of three different joining processes to take place.

Process #1 Softening and Crimping-

Material is heated until soft, then crimped with enough pressure to form a bond that will not fail, when tested for shear or tensile failure. Rolling, staking, pinching, bending, crushing, or stapling and pining using another material. This method relies on a mechanical bond and not an adhesive or welded bond.

Process #2 Heating and Welding-

Material is heated to a sufficient temperature to enable the both profiled sheet members to be fused as one through the commingling of material from each member. The bond relies on both the geometry of the profile and the size and depth of the weld line for strength of the joint.

Process #3 Fusing with Added Material-

Material may or may not be heated and a third component or more, is added to promote the fusion process. The interlocks can be mechanically manipulated in an efficient manner to effectively add bonding or welding material. If heated, the temperature to which the profiled members are heated is dependant on what the bonding mechanism of the remaining component is trying to promote. The bond may be adhesive, mechanical, or fusion in nature. Crimping may be used to improve the quality of the bond. Solvent or other adhesive may be used provided the interlocks have been distorted sufficiently to provide enough surface contact for the added component to work. Addition of an adhesive would normally be considered expensive and not a process of great commercial value but still may be used. The bond may be either adhesive or welded in nature.

Process #3 Fusing “Cold” by Pressure Pressure is applied to the “cold” portions to bond them together.

Equipment

The equipment is of such design as to accept lengths of extruded profile as may be required for the end use. The profile members may or may not be pre-assembled but not fused together. The equipment is of such a design that when the members are subjected to the operation a monolithic single member emerges.

Two basic equipment designs may be used to fuse the profiles, progressive method or a batch method.

The progressive method provides that the equipment to use a series of feed mechanisms whereby the profile interlocks are heated, re-formed, or otherwise fused in continuous pass-through operation. The design consists of conveyers, rollers, belts or tracks, and both a means to heat and cool the profiled material. This allows for profile members of undetermined length to be processed on a single piece of equipment.

The batch method requires that the equipment be designed with the maximum length of profile seam to be predetermined. The edge is heated and the secondary fusing operation is performed on the entire edge at once. This method offers that higher processing rates are possible. The heating operation can be performed on the entire edge without subjecting the material to excessive temperature causing damage to the polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view one section of sheet piling; and

FIG. 2 is a perspective front view of two sheets of FIG. 1 welded together.

FIG. 1 is a perspective view of one Z Shaped section of plastic piling. This section shown generally at 3 has shaped interlocks 1 and 2 formed at either end. The structure of the interlocks may be any desired interlocking shape. FIG. 1 shows two Z Shaped sections 3 and 4. Section 4 is identical to section 3 and has interlocks 5 and 6 formed at the ends thereof. The weld area in the manner described in accordance with this invention is denoted 7.

The need for this invention is clear for any person who is skilled in the art of soil retention, sheet pile devices. By taking advantage of different plastic fabrication fusion techniques and new machine control technology small individual and generally inexpensive soil retention barriers can be used to create a single much stronger barrier. Installation is easier, and thus less expensive than two single sheets. Since the manufacture is less capital intense more product size variations can be made available.

Further modifications to the methods and apparatus of the invention may be made without departing from the spirit and scope of the invention. 

1. A method of making thermoplastic sheet pile comprising the steps of: forming at least two sections of Z-Shape thermoplastic pile; heating portions of both of said sections to a predetermined temperature to avoid damage to the materials; and joining said heated portions together.
 2. The method of claim 1 wherein said joining of said heated portions is done by crimping the heated portions with enough pressure to form a bond.
 3. The method of claim 1 wherein said joining of said heated portions is done by rolling, staking, pinching, bending crushing, or stapling and pinning using another material.
 4. The method of claim 1 wherein said joining of said heated portions is done by welding to cause the co-mingling of material from each portion.
 5. The method of claim 1 wherein said joining of said heated portions is done by fusing using one or more additional material to promote fusion.
 6. The method of making thermoplastic sheet pile comprising the steps of: forming at least two sections of Z-Shape thermoplastic pile; applying pressure to portions of both of said sections to avoid damage to the materials and to join said portions together. 